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Thousands die from flu every year in SA – how does the common flu virus compare to the new coronavirus?

Since January 2020, the outbreak of the virus which causes Covid-19, has had the world in a tizz. While it has already spread to more than 60 countries around the world, South Africa remains spared.

But should we be concerned, and is this new coronavirus more worrisome than the seasonal flu? Professor and Head of the Division of Medical Virology at the University of Stellenbosch, Wolfgang Preiser, and Professor Keertan Dheda, Head of Division of Pulmonology at the University of Cape Town, explains:

Coronavirus vs. flu: which is deadlier?

More than 3 000 people have died globally and over 88 000 have been infected with the Covid-19 virus, according to CNN

On the other hand, influenza (commonly known as the flu) statistics paint an even bleaker picture: the World Health Organization (WHO) estimates that worldwide, annual flu epidemics result in as many as five million cases of severe illness, and about 290 000 to 650 000 deaths. 

To put it in a local context, the flu kills between 6 000 to 11 000 South Africans every year, according to the National Department of Health. About 50% of those deaths are among the elderly, and about 30% in HIV-infected people. 

To put this into further context, an article by the New York Times reports that the seasonal flu strains kill about 0.1% of people who become infected, whereas early estimates of the coronavirus death rate from Wuhan, China are around 2%.

However, we should be cautious to label this the “true death rate” for two reasons: 

  • Many mild-symptom or symptom-free cases are not detected.
  • The sudden outbreak was hard to control and contain in the beginning – although it bought the rest of the world time to prepare for the dissemination of the virus.

This means that the actual death rate could be under 2%, and similar to that of a severe seasonal flu, below 1%, according to an editorial published in the National Institute of Allergy and Infectious Diseases.

Is the flu more contagious than the coronavirus?

Although data from China shows that it is more contagious than influenza, we should bear in mind that at this point, the actual risk of infection isn't any higher per se, and that it’s simply about the spread being quicker, Orly Vardeny, associate professor of medicine at the Minneapolis VA Health Care System and University of Minnesota said.

And unlike in the case of the flu, there's no vaccine yet.

According to the New York Times, a person infected with the Covid-19 virus appears to infect 2.2 people, on average, whereas for the seasonal flu it’s 1.3. But, again, the new coronavirus figure is skewed by the way in which the disease was handled in the beginning. As it comes under control, so will this figure subsequently drop.

For now, the flu still presents a greater danger, explains Professor Preiser:

“We should be more concerned about the flu [than we are] because every year, in South Africa alone, it kills more than 11 000 people, and much of that could be prevented if people had themselves vaccinated.

“Vaccinating against flu, especially this year, means that you will potentially be less of a burden to the healthcare system, and avoid being flagged as a possible coronavirus case.”

Similarities and differences between influenza and the virus that causes Covid-19

Officials at the WHO this week sought to differentiate between the new coronavirus from influenza, with WHO Director-General Tedros Adhanom Ghebreyesus explaining the following at a briefing on Tuesday:

  • Both the new coronavirus and seasonal flu cause respiratory disease.
  • Both spread the same way, via small droplets of fluid from the nose and mouth of someone who is sick.
  • However, based on current data, the new virus does not transmit as efficiently as influenza.
  • With this new virus, it appears you have to be sick to transmit it to someone else. With influenza, people who are infected but not yet sick are major drivers of transmission.
  • The Covid-19 virus causes more severe disease than seasonal flu.
  • More people are susceptible to being infected with the new virus than the flu, and some will suffer severe disease. This is because many people have built up immunity to seasonal flu strains, whereas the Covid-19 virus is new - and a virus to which no one has immunity.
  • Globally, seasonal flu generally kills far fewer than 1% of those infected. By comparison, about 3.4% of reported Covid-19 virus cases have died. 
  • Vaccines are available for seasonal flu, but not for the new vrus. However, more than 20 vaccines are in development.
  • Containment for the new virus is possible, but not for seasonal flu.

Who is most at risk from infection?

A recent article by Health24 notes that this new virus which causes Covid-19 is striking men and older people the hardest. Experts agree that the latter is happening because older people have immune systems that wind down as they age and therefore become less effective, making them more prone to dangerous viral strains (much like as the department of health stats show, roughly 50% of flu-related deaths in South Africa are the elderly).

And having a chronic illness – like arthritis, diabetes and heart disease – means that the body is less able to cope with infection.

On the question of why the virus is attacking men more than women, research has shown that, in China, many more men smoke than women. In fact, more than half of Chinese men smoke, compared with only around 3% of women. 

Smoking activates a receptor used by the coronavirus to infect human cells, ACE-2, Dr Greg Poland, a vaccine researcher and infectious disease specialist with the Mayo Clinic, in Rochester, Minnesota said, although this is speculative at this stage.

However, Preiser weighed in and explained that if someone's lungs are affected by smoking (in a way, a chronic illness), then that certainly increases the risk from a virus that affects the lungs as “one has 'fewer reserves' to fall back on when the lungs are infected and inflamed”, he said.

Dheda adds: "Smokers are at higher risk of contracting many respiratory tract infections including influenza, TB, and Streptococcus pneumoniae, an important cause of acute pneumonia." 

"There are a number of mechanisms by which cigarette smoking does this, including subverting the defensive functions of the airway lining and various types of immune defensive cells including macrophages and lymphocytes."

Are those living with HIV and TB at a higher risk of infection?

"Anyone with underlying immunodeficiency or weakened lung defenses will be more susceptible to respiratory pathogens, including the new coronavirus," says Dheda.

"So individuals who are HIV-infected and those with substantial post-tuberculous lung disease would be more susceptible to contracting coronavirus."

Preiser also says that we should take into consideration that the places affected so far have far fewer HIV-positive people than we have, however, "it needs to be assumed (until proven otherwise – which is unlikely) that if you have HIV, or TB, or any other chronic illness, your risk of severe coronavirus disease is increased.”

Protecting yourself

Although there is currently no vaccine or “cure” for the new virus, there are preventative measures you can take to minimise your risk of contracting the virus:

  • Avoid coming into close contact with people who are ill.
  • Wash your hands with soap and water frequently and thoroughly. 
  • Make it a habit to clean and disinfect furniture that is frequently touched.
  • Cover your face with a tissue or your elbow when coughing or sneezing.
  • Visit a doctor if you develop symptoms.

Image: iStock

Thousands die from flu every year in SA – how does the common flu virus compare to the new coronavirus?